1. Field of the Invention
This invention generally relates to a power control technique, and more specifically, to a power discharge control system applicable to an electronic device for eliminating residual voltage of each electronic component therein.
2. Description of Related Art
Discharge circuit is commonly disposed in modern electronic devices, e.g. personal computer, server, etc., thereby enabling the electronic device to discharge residual power from operation power provided for each electronic component therein when power supply of the electronic device is in a power off state.
Referring to FIG. 1, a circuit of an existing power discharge control system is illustrated. As shown in the figure, the power discharge control system 10 is used on an electronic device having a power supply 11, wherein the power supply 11 serves the purpose of providing each electronic component 13 inside the electronic device with various types of operation power, such as 5V and 3.3V. Furthermore, the power supply 11 has a power discharge control pin (N12V) 111 for outputting the respective low level electrical signal and high level electrical signal that correspond to power on and power off states of the electronic device.
As shown in the figure, the power discharge control system 10 includes a plurality of dissipative resistors 101 electrically connected to the power supply 11 (in the figure, the dissipative resistor 101 includes two fixed resistors connected in parallel, but not restricted to as shown herein), wherein a switch unit 105 and the plurality of dissipative resistors 101 are electrically connected to the power discharge control pin 111 (as shown in the figure, the switch unit 105 is an n-channel Junction Field Effect Transistor (JFET)), a gate of the switch unit 105 (JFET) is electrically connected to the power discharge control pin 111, a drain of the switch unit 105 is electrically connected to the dissipative resistors 101, and a source of the switch unit 105 is grounded. After the electronic device is turned off, the power discharge control pin 111 immediately outputs a high level electrical signal to the gate of the switch unit 105, thereby turning on the switch unit 105, and consequently providing the operation power of the power supply that is electrically connected to the dissipative resistors 101 with a power discharge path to ground, so as to achieve the objective of residual power discharge of the electronic devices.
As the technology advances, new models of power supply have also been developed. However, new power supply models are not equipped with said power discharge control pin 111. Hence if said power discharge control system 10 is adopted, it is obvious that the current system is not capable of eliminating residual voltage of electronic device when the power supply is turned off. As there is no other compatible power discharge control system, when the power supply is in a power off state, residual power of the electronic device can only be released by means of spontaneous power consumption, and spontaneous discharging speed depends on disposition of each electronic component that receives operation power from the power supply 11. Generally, spontaneous discharging speed is slower, and consequently, the residual voltage will remain inside the electronic device for a longer period during the power off stage. The residual voltage will further cause some electronic components inside the electronic device to operate erroneously, thereby resulting in an adverse effect on operations of the electronic device at the subsequent power on. Besides, the operation time of each electronic component is indirectly prolonged due to the aforementioned error, and as a result, the life span of each electronic component is further decreased.
Hence, it is a highly urgent issue in the semiconductor industry to design an effective device to provide a power discharge control system that is capable of solving the drawbacks of the aforementioned technique.